A conventional radial ply tire has a single carcass ply extending between a pair of axially spaced bead cores which is wrapped about each bead core having axially outer ply turnup ends. This construction has the main working part of the ply turned inside of a bead apex forcing a curvature in the ply path when the tire is mounted onto a rim. This curvature gives the radial tire a fat bulging appearance in the tire footprint when under load.
Attempts to avoid this sidewall curvature change about the bead and bead apex have led some to attempt a ply path that wraps about the bead and has the turnup end wrap inside of the bead and bead apex. In this construction the turnups are positioned inside the beads and the ply path avoids the normal curvature change. This provides a better performing tire in terms of bead area durability and overall tire performance.
Unfortunately, such a tire when made with a single carcass ply is difficult to mass produce because the inside turnups are not conducive to conventional tire building.
In U.S. Pat. No. 6,913,052 B2 assigned to The Goodyear Tire & Rubber Co., a split ply structure and method of manufacture was proposed wherein inextensible steel plies could be made with inside turnups. The advantages being improved bead durability and significantly reduced weight reduction. In this patent the method of building the tire having a carcass assembly having a pair of bead cores and a radial ply reinforcing structure has the steps of cylindrically applying a pair of radial cord reinforced sidewall plies, each sidewall ply having a width Wp; setting one bead core over each sidewall ply and fixing the axial spacing between the bead cores at a distance L; applying a crown ply having a width WC, WC being less than the distance L and the crown ply being interposed between and spaced from each sidewall ply when applied; turning up each sidewall ply to fold over and overlap the lateral edges of the crown ply; moving the carcass assembly axially inwardly while shaping the carcass assembly toroidially to form ply turnups axially inward of the bead cores. The step of stitching the overlap of the sidewall plies to the crown ply is recommended. Once toroidially shaped the method can further include applying a belt reinforcing structure to the toroidially shaped carcass, the first belt reinforcing layer having a width WB, the first belt layer overlaps the radially outer ends of the sidewall plies. Then an additional one or more belt reinforcing layers can be applied to the carcass as well as applying the tread.
This method of cylindrically forming the split ply carcass as a complete stage 1 assembly allowed the second stage toroidal assembly of the belts and tread similar to conventional tire building.
The method and resultant prior art tire while novel did not take full advantage of the split ply features and as a practical matter was not that different from conventional tire building.
The present invention discloses a new and unique assembly of a bead area monocomponent that can be made as an intermediate article of manufacture in a first stage building method and then can be assembled later as an intermediate article of manufacture into a second stage toroidaly shaped green split ply carcass assembly along with the belt structure and tread to form an uncured tire assembly.
The present invention has the objectives of allowing a simplified assembly of the bead area monocomponents; provide allowance for a range of tire sizes to be made from one size of the monocomponent; the method employs a molded hub device for bead carrying and centering as well as holding the completed intermediate articles of manufacture for storage once formed as a subassembly. These and other objectives are disclosed as follows.